Electric fuse



Jan. 1a, 1938. G. GooDwm 2,105,591

ELECTRIC FUSE Filed June 19, 1935 Patented Jan. 18, 1938 UNITED STATES PATENT OFFIQE ELECTRIC FUSE Application June 19, 1935, Serial No. 27,313

14 Claims.

This invention relates to electric fuses and, in certain aspects, more particularly to such fuses of the plug type.

One object of this invention is to provide a fuse of cheap construction and yet which is reliable and eiiective.

Heretofore it has been usual to make certain portions of plug fuses of porcelain, and when glass tops have not been used, to attach windows of mica or the like over the top ends of the porcelain members as by metal ferrules. One of the disadvantages of this construction is that the porcelain parts cannot be made commercially to accurate dimensions and this adds to the difiiculty and expense of assembly. Another disadvantage is that metal parts are exposed for engagement with the fingers where mica windows have been employed, and while this metal is out of contact with any electrical parts and actually presents little possibility of danger, yet many people do not like to touch metal parts of electrical apparatus.

One object of the present invention, therefore, is to produce a construction wherein material moldable to exact measurements may be employed and wherein metal parts are not positioned where it is necessary to touch them when removing or replacing the fuse by hand.

A further object is to provide a construction by which assembly and securement of the parts is facilitated.

Another object is to provide visual indication of the condition of the fuse, whether bad or good, which will give a direct indication, instead of indicating by changes in appearance only, which are not always understood by one not familiar with fuses.

For a more complete understanding of this invention, reference may be had to the accompanying drawing in which Figure 1 is a perspective of a plug fuse constructed in accordance with this invention.

Figure 2 is a central vertical section to a larger scale on line 22 of Figure 1.

Figure 3 is a section on line 3--3 of Figure 2.

Figure 4 is a top plan of the fuse.

Figure 5 is a detail section on line 5-5 of Figure 2.

Figure 6 is a fragmentary perspective of a fuse link.

Figure 7 is a view similar to a portion of Figure 3, but showing a modification.

Figure 8 is a perspective of a portion of the same construction.

Figure 9 is a view partly in section similar to Figure 2, but showing a further modification.

Figure 10 is a. fragmentary perspective showing the fuse link and indicator of Figure 9.

Referring first to Figures 2 and 3, at I is indicated a casing of insulating material, such, for example, as a moldable composition of a synthetic resin or the like, such material being capable of being molded to precise dimensions. This casing is provided with an upper portion 2 of relatively large diameter, terminating in a rim 3 which may be roughened on its outer side as at 4 (see Figure 1) to facilitate engagement of the fuse by the fingers for screwing into and out of its threaded receptacle. of the casing is of reduced diameter as at 5 and is partly closed off at its lower end by a base 6 having a central hole or perforation "I therethrough.

The top of the casing l on its inner side is of enlarged diameter or counterbored as at 8 to form a shoulder 9 on which may rest a window member ID of mica or other suitable transparent material. Above the shoulder 9 is positioned an inwardly extending lip l l, which, as shown best in Figure 4, is not continuous but may be formed of segmental portions with intervening spaces as at 13. By so forming the lip it may be molded in place, the portions i3 permitting the removal of the molded casing from the mold in which it is formed. This lip H i'orms means for retaining in position a disk 14 which may be made of thin metal dished inwardly to forms. flaring rim i5 which is preferably formed with serrations I6 about its margin. By forcing this 5 disk inwardly after the window member 10 has been placed in position, the marginal edges of this disk at the rim 15 may be sprung in under the lip l I. This acts to firmly retain the window in position and it cannot be readily removed thereafter, and it is quite capable of withstanding all the pressure which is exerted within the fuse casing when the fuse blows, such pressure acting to expand the rim 15 into closer engagement with the internal wall of the casing i immediately below the lip H. n

For engagement with the interior threads of the socket in which such a fuse is placed, a threaded metal shell 2t; is employed, the upper unthreaded edge 2| of which may engage in a slightly reduced diameter portion 22 in the outer face of the portion 2 of the casing i. The lower end of the shell 20 is iii-turned as at 32 and extends beneath and in contact with the base 6 of the casing. This base 6 is preferably provided The lower portion i with notched out of portions as at 23 into which the material of the shell may be pressed as at 24 to lock the shell 22 against rotation with the casing I so that by rotation of the casing I between the fingers, the shell may be screwed into or out of its socket.

At 25 is indicated a fuse link which is shown as provided with an intermediate upwardly looped portion 26 provided in its top portion with a reduced cross section part 2". to localize the point of rupture of the link when the fuse blows. One of the downwardly extending end portions of the fuse link such as 28 passes downwardly through a perforation 29 in the annular portion 30 of the casing and into the space between the inner face of the shell 20 and the outer face of the reduced diameter portion 5 of the casing I. At its lower end the portion 28 passes between the base 6 of the casing and the shell 20 and its extreme end is folded about the inner edge of this shell, passing downwardly through a central opening thereof. The opposite end portion 3'! of the fuse link is turned inwardly and is formed as an annulus 38, resting upon the top of the base ii of the casing l. These parts are all secured together by a rivet M which is shown as tubular and which passes through an insulating washer 4|, through the opening '1 of the base 8 and through the annulus 38 and is headed over onto the top of this annulus. This not only secures the inner end of the fuse link to the upper face of the casing base 8, but also clamps the opposite folded end of the fuse link about the lower edge of the shell 20 out of electrical connection with the rivet 40. The rivet 40 likewise serves as the central terminal of the fuse, the shell 20 forming the other terminal.

In order to facilitate the insertion of the fuse portion 28 into the proper position, the interior wall of the upper portion 2 of the casing is provided with a pair of guide lugs (see Figures 3 and 5), having their top edges rounded off, to serve as a guiding channel into which the fuse end 28 may be placed and by which this end is guided down through the opening 29 as far as may be permitted by stop extensions 280 on the portion 28. The shell 20, casing l, fuse element 25, and the washer 4] having been assembled, the rivet 40 is inserted in position. By heading over the rivet 40, these several parts are secured together in correct position, after which the window l0 and its retainer 12 may be placed in position.

In order to give a positive indication of the condition of the fuse element as to whether or not it is blown, means such as shown in Figures 2 and 3 may be employed. Referring to these figures, at is shown a leaf spring element which may be secured at one end as at 5| in any suitable manner to the casing i. As shown its end portion is bent to the shape of the casing wall and its extreme end 52 is inserted in a perforation 53 in the portion 30 of the casing. This spring is looped upwardly and at its upper end is bent to form a hook portion 54 into which is inserted an indicating card 55. Below this card the spring 50 bears against one side edge of the fuse link 25 so that when the fuse link blows, the spring 50 is free to unbend somewhat so as to move the indicator card 55 laterally from its normal position before the fuse link was blown. The window retaining disk [4 is shown as provided with an opening 56 through which a portion of the window is exposed and when the card 55 is in its normal condition before the fuse is blown, a portion of it is positioned back of the perforation 55, this showing therethrough a legend such as good indicating that the fuse link has not blown. On the blowing of the fuse link the spring 50 is released, thus moving the legend good out from registry with the opening 56 and presenting another portion of the card in register therewith on which portion may be shown the legend bad, indicating that the fuse link has blown.

In Figures '7 an: 8 another type of indicator is shown in which a spring 50, similar to the spring 58 shown in Figures 2 and 3, is employed and which normally rests against one side edge of the fuse link 25. The upper end of the spring 60, however, is curved over to loosely engage one end of a tilting indicating member 65, which, as shown in Figure 8, is pivoted within a slot 66 in a partition member 61 which may be seated on a plurality of annular shoulders 68 which integral with the casing wall. The indicator 65 may have its ends notched as at Til so as normally to be retained in rocking position in the partition 61 and normally present one face upwardly toward the opening 56 in the window retainer,

this face having an indication such as good, showing the fuse in workable condition. soon as the fuse blows and releases the upper end may be of the spring 69, the indicator 65 is turned about its axis to present its opposite side uppermost, i

this side showing the bad indication as shown in Figure 8, so that this bad indication is visible through the window and the opening 55 of the window retainer.

With either of these forms of indicator, the

recesses 23 and the depressions 24 of the casing and shell, respectively, hold the parts in their desired relationship with the spring 50 or 66 at substantially right angles to the plane of the fuse link.

In Figures 9 and 10 a different form of indicator is employed in which the spring '15 is arranged in the plane of the fuse link and acts to separate the two portions of the fuse link when it blows at its reduced diameter portion 21. 1

This spring '15 is shown as supporting the indicator card 16, which when the fuse link is whole presents a good indication opposite to the opening 56 of the window retainer and after the fuse has been blown presents the bad indication.

From the foregoing description of certain embodiments of this invention, it should be evident to those skilled in the art that various changes and modifications might be made without departing from the spirit or scope of this invention as defined by the appended claims.

I claim:

1. A fuse comprising a casing, a threaded metal shell, a fuse link, and a fastening element securing said casing and shell together and one end of said fuse link about an edge of said shell.

2. A fuse comprising a casing, a threaded metal shell, a fuse link, and .a fastening element securing said casing and shell together and one end of said fuse link about an edge of said shell, said element also securing the other end of said link to said casing.

3. A fuse comprising a casing, a threaded metal shell, a fuse link, and a fastening element secur ing said casing and shell together and one end of said fuse link to said shell, said element also securing the other end of said link about an edge of said casing and itself forming a fuse terminal.

4. A fuse comprising a tubular casing having its lower portion of reduced external diameter, a threaded metal shell spaced from said reduced portion and having its lower end in-turned beneath said lower portion, and a fuse link, said casing having a hole therethrough leading into said space, and said fuse link extending through said hole and secured about an edge of said shell.

5. A fuse comprising a tubular casing having its lower portion of reduced external diameter, a threaded metal shell spaced from said reduced portion and having its lower end in-turned beneath said lower portion, and a fuse link having its end portion folded over the inner edge of said shell, said casing having a hole therethrough leading into said space and said fuse link extending through said hole into said space, and means clamping said end portion, shell, and casing together.

6. A fuse comprising a tubular casing having its lower portion of reduced external diameter, a threaded metal shell spaced from said reduced portion and having its lower end in-turned beneath said lower portion, and a fuse link having its end portion folded over the inner edge of said shell, said casing having a hole therethrough leading into said space and said fuse link extending through said hole into said space, and means clamping said end portion, shell, and casing together, said clamping means comprising a terminal for the other end of said link.

7. A fuse comprising a tubular casing, a threaded metal shell having its lower end in-turned beneath the lower portion of said casing, a fuse link having its end portion folded over the inner edge of said shell at its lower end, and means for clamping said fuse link shell and casing together.

8. A fuse comprising a casing, a threaded metal shell having an end inturned over an end of said casing, an insulating washer engaging the outer face of said inturned end, a fuse link in said casing having one end engaged between said washer and casing and in contact with said shell, said shell having an opening through said end, and a rivet extending through said opening and said washer and engaging the opposite end of said link for securing said casing, shell, fuse link and washer together, said rivet also serving as a terminal for said fuse link.

9. A fuse comprising a casing, a threaded metal shell having an end inturned over an end of said casing, an insulating washer engaging the outer face of said inturned end, a fuse link in said casing having one end engaged between said washer and casing and bent about the edge of said shell, said shell having an opening through said end, and a rivet extending through said opening and said washer and engaging the opposite end of said link for securing said casing, shell, fuse link and washer together, said rivet also serving as a terminal for said fuse link.

10. A plug fuse comprising a casing of insulating material having an open upper end and a lower end provided with a central opening, a threaded metal shell having its upper edge engaging the side of said casing and its lower end inturned beneath the lower end of said casing and having an opening therethrough, said shell and casing having a space therebetween, a fuse link having a loop portion upstanding within said casing, said casing having an opening therethrough extending into said space and through which one end portion of said link extends, the end of said portion engaging about the edge of said shell at said shell opening, an insulating ring beneath said shell, a rivet extending through said ring and central casing opening and clamping said in-turned shell end to the outside of said casing out of electrical connection with said rivet and the opposite end of said link to the inner side of said casing and in electrical connection with said rivet, and a window secured in the open upper end of said casing.

11. A fuse comprising a casing having an open top provided with a counterbored portion having an inwardly extending lip spaced from the base of said portion, a window member seated in said counterbored portion, and a downwardly dished member having an opening therethrough for exposing a part of said window and sprung into position beneath said link and retaining said window in position.

12. A fuse comprising a casing having an open top provided with a counterbored portion having an inwardly extending annular lip spaced from the base of said portion, a window member seated on the base of said counterbored portion beneath said lip, and a window retainer dished inwardly to form a flaring annular rim sprung in and engaging beneath said lip and bearing on said member.

13. A fuse comprising a casing having an open top provided with a counterbored portion having an inwardly extending annular lip spaced from the base of said portion, a window member seated on the base of said counterbored portion beneath said lip, and an inwardly dished thin metal member having a flaring annular rim sprung in and engaging beneath said lip and bearing on said window member.

14. A fuse comprising a casing having a window, a fuse link in said casing and. having a weakened portion, a leaf spring bearing against said link and having one end secured whereby when said fuse parts at said weakened portion a portion of said spring is freed for motion away from its normal position, and a fuse-condition indicator pivotally secured in said casing to present either of two faces to view through said window in position to be turned about its pivot by said spring motion and present the face indicating that the fuse has blown.

GEORGE GOODWIN. 

